Ok, I get it — HTTPS has nothing to do with this specifically. But this encryption mechanism (custom packet encryption or session-based encryption) does play a crucial role in securing the communication between the L2 client and the L2JMobius server, especially when it comes to protecting sensitive information like passwords during the login process.
Without such encryption in place, passwords and other sensitive data could be intercepted by an attacker. So does something like this already implemented there or I have to do it?
Edit* With a simple wireshark sniffing I was able to retrieve the username and the hashed/encoded password that is being transmitted during the login process.